Dual Mandrel Sidewall Image Transfer for Sublithographic Patterning
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Solution Overview
Problem
The scaling of lithographically printable dimensions is stagnating due to delays in developing lithographic exposure tools for printing small-scale images, necessitating methods to form small dimensions beyond lithographic capabilities, particularly for patterning complex and arbitrary patterns in semiconductor manufacturing.
Innovation Solution
A method involving dual mandrel sidewall image transfer processes, where two lithographically patterned mandrels with spacers are used. The spacers intersect or contact each other, and portions are etched using an etch mask, allowing for the transfer of a composite pattern into a material layer, enabling sublithographic dimensions and complex patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional lithographic methods are used to form patterns, then the manufacturing process is simple and direct, but the minimum printable dimension is limited and cannot achieve sublithographic dimensions
Solution Approach 1:
The patterning process is divided into multiple sequential steps: forming a first mandrel structure with first spacers, then forming a second mandrel structure with second spacers. Each mandrel-spacer pair creates a portion of the final pattern, allowing complex sublithographic patterns to be built incrementally rather than attempting to print them all at once.
Solution Approach 2:
The second mandrel structure is formed to straddle the first spacer, and the second spacer is formed around the second mandrel structure. This nested arrangement where structures are formed around and upon previous structures enables the creation of composite patterns with dimensions smaller than the lithographic limit.
2Adaptability or versatility
If lithographic capabilities are used to pattern structures, then the process is straightforward, but complex and arbitrary patterns cannot be formed
Solution Approach 1:
The complex pattern is segmented into multiple simpler patterns formed by different mandrel-spacer combinations. The first mandrel structure and first spacers create one pattern element, while the second mandrel structure and second spacers create another element that intersects with the first, together forming the complex arbitrary pattern.
Solution Approach 2:
The patent transitions from two-dimensional lithographic patterning to three-dimensional spacer-based patterning. By forming spacers around mandrels and allowing them to intersect, the process exploits the vertical dimension and spatial relationships to create complex patterns that cannot be achieved with planar lithography alone.
3Manufacturing precision
If single mandrel sidewall image transfer is used, then the process is simpler, but the achieved pattern dimensions are still constrained by lithography
Solution Approach 1:
The second mandrel structure is formed to straddle the first spacer, creating a nested configuration. The second spacer is then formed around the second mandrel structure, with the two spacers intersecting and contacting each other's sidewalls. This nesting enables dimensional multiplication beyond single-mandrel capabilities.
Solution Approach 2:
The patent merges two separate sidewall image transfer processes into a single integrated flow. The first spacer and second spacer are both formed and patterned together, with their sidewalls contacting to provide a combined thickness equal to the sum of individual spacer thicknesses, achieving dimensions unattainable by either process alone.
Data Source
AI summary
A combination of two lithographically patterned mandrels can be employed in conjunction with sidewall spacers to provide two spacers. The two spacers may intersect each other and/or contact sidewall surfaces of each other to provide a thickness that is a sum of the thicknesses of the two spacers. Further, the two spacers may be patterned to provide various patterns. In addition, portions of at least one of the two spacers may be etched employing an etch mask. Additionally or alternately, an additional material may be selectively added to portions of one of the two spacers.